Abstract To understand how the microtubule motors, cytoplasmic dynein and kinesins, find and transport cargoes to specific cellular destinations, we need to know much more about how motors are attached to cargoes. The extended morphology of axons and dendrites makes post-mitotic neurons especially dependent on polarized transport and ideal for studying the regulation of transport. We recently showed that -spectrin mutations in humans that cause spinocerebellar ataxia type 5 (SCA5) impair motor-based transport of synaptic vesicles in a Drosophila model of neurodegeneration. In this application, we focus on an analysis of -spectrin and it's role in mediating the attachment of dynactin and cytoplasmic dynein to cargoes in neurons. We will characterize the defective neuronal transport in our fly model and will pursue the gene products and mechanisms that regulate transport. The selective use of the proposed spectrin/ motor linkage in will be studied in the axons and dendrites of living neurons (Aim 1). New genetic modifiers of the SCA5 phenotypes and neuronal transport will be characterized in motility and biochemical assays (Aim 2), and the connection between neuronal transport, autophagy and neurodegeneration will be explored (Aim 3). Our work has important long-term implications for the understanding and treatment of spinal cord injuries, and the family of neurodegenerative diseases, including Amyotrophic lateral sclerosis, Huntington's Disease, and Alzheimers Disease.